Three experiments are proposed in continuation of studies of nutrient-behavior interactions in children. Based upon current data, the theory is proposed that carbohydrate/protein intake reflects changing energy needs during periods of rapid brain growth and stress. But the unregulated intake of carbohydrates has deleterious effects upon performance. Quantitative measures of brain electrical activity, attention, and plasma amino acid ratios are proposed as measures for examining the hypothesized relationships as they change across critical age spans (6-8, 8-10, 10-12 years), in normal and psychiatrically impaired children. Glucose levels have not been predictive of observed changes in activity level and cognition during challenge experiments. We propose that insulin/glucose ratio regulates the increase or decrease in activity levels. This idea is tested by comparing doses of glucose which have different insulin/glucose ratio effects. Aspartame, a new artificial sweetener, may cause serious behavioral effects in young children. It is proposed that such changes reflect changes in brain and plasma tyrosine levels. An experiment is proposed with 4-year old children in which combinations of glucose and aspartame are compared with aspartame and glucose alone. Plasma amino acid ratios are examined, as well as cognitive and activity changes.